1. Field of the Invention
The invention relates to a nonaqueous electrolyte secondary battery and to a method for producing the battery. In this Specification, a “secondary battery” refers to a conventional battery that can be repeatedly charged. A “nonaqueous electrolyte secondary battery” refers to a secondary battery that uses a nonaqueous electrolyte that contains a nonaqueous solvent in which an electrolyte salt is dissolved. A “lithium ion secondary battery”, which is a type of “nonaqueous electrolyte secondary battery”, refers to a secondary battery that uses the lithium ion as an electrolyte ion and that implements charge/discharge by the movement of charge associated with the lithium ion between the positive and negative electrodes. The lithium ion secondary battery in this Specification can encompass the batteries generally referred to as “lithium secondary batteries” (for example, lithium ion polymer secondary batteries).
2. Description of Related Art
Here, for example, Japanese Patent Application Publication No. 2010-113920 (JP 2010-113920 A) discloses a lithium ion secondary battery provided by the introduction into a battery case of an electrolyte solution having a higher lithium ion concentration than the electrolyte solution disposed between the positive electrode active material layer and the negative electrode active material layer. This lithium ion secondary battery makes it possible—even when high-rate charge/discharge is carried out—to suppress reductions in the lithium ion concentration of the electrolyte solution disposed between the positive electrode active material layer and the negative electrode active material layer and to thereby suppress increases in the battery resistance.